This invention relates to communication network services for transporting ATM (Asynchronous Transfer Mode) cell traffic over IP (Internet Protocol) based networks, and particularly to ATM-coupled multicast service over IP networks.
IP multicasting involves the transmission of IP datagrams to a xe2x80x9chost groupxe2x80x9d, a set of zero or more hosts identified by a single IP destination address. Internet forwarding of IP multicast datagrams is handled by xe2x80x9cmulticast routersxe2x80x9d which may be co-resident with or separate from the internet gateways. Multicasts save bandwidth by routing a single datagram once through an IP backbone from the backbone to a multiplicity of destinations.
Because ATM and IP protocols are mainly incompatible, it is difficult for ATM systems to partake of the advantages of the IP multicasting. The aforementioned application Ser. No. 09/400,609 filed Sep. 20, 1999 discloses transmission of each ATM cell in a single IP packet over an IP backbone. However, this still does not offer the advantages of multicast service.
According to an embodiment of the invention, ATM-connected multicast data are transmitted to a multiplicity of ATM users over an IP backbone by having a controller in the IP backbone translate a pre-stored Multicast Initiating Address into a multiplicity of pre-stored pairs of addresses, each pair composed of a user""s ATM destination address and the IP address of the (user) gateway serving the user""s ATM destination, then establishing connections between the multicast source ATM address and each of the user""s ATM addresses, encapsulating the multicast data ATM cells in IP packets for routing to the user gateways, and decapsulating the multicast data ATM cells for transmission to the user ATM addresses.